Re: [Bug-tar] GNU tar 1.15.1, format gnu, multivolume failure

[Joerg Schilling]

John Gatewood Ham <address@hidden> wrote:

> GNU tar maintainers,

> > From the info file:
> "gnu
>         Format used by GNU `tar' versions up to 1.13.25. This format
>         derived from an early POSIX standard, adding some improvements
>         such as sparse file handling and incremental archives.
>         Unfortunately these features were implemented in a way
>         incompatible with other archive formats.
>
>         Archives in `gnu' format are able to hold pathnames of unlimited
>         length."
>
> May I suggest instead: "Archives in `gnu' format are able to hold
> pathnames of unlimited length when you do not use the multi-volume
> option."

If you change this, then it would ne adequate to fix the rest of the text too:

        Format used by GNU `tar' versions up to 1.13.25. This format
        is a non POSIX compliant extension to a tar implementation
        done by John Gilmore which did implement a subset of the POSIX
        standard at that time. The improvements such as sparse file
        handling and incremental archives have been done by an incompatible
        reuse of the prefix field from the POSIX standard.

If you like to stay with the old text, please send an evidence that
proves the existence of such ealy POSIX draft that does not include the prefix
field. My POSIX draft from spring 1987 includes the prefix field and
the incompatible extensions have been added in 1989.

>
> First I tried --format=posix since all your documentation says use
> it.  That does not do multivolume backups.  I found that documented
> in the TODO file, but not in the main info file.  The error message
> was not helpful in this case.  On the chart where you compare
> features you should have this instead I think:
>
> "Format  UID            File Size      Path Name      Devn      Multiple
>                                                                    Volumes
>     gnu     1.8e19         Unlimited      Unlimited      63        Yes **
>     oldgnu  1.8e19         Unlimited      Unlimited      63        ?
>     v7      2097151        8GB            99             n/a       No
>     ustar   2097151        8GB            256            21        ?
>     posix   Unlimited      Unlimited      Unlimited      Unlimited No
>
> ** WARNING: the last file name on a volume in a multi-volume archive
>                member must be strictly less than 129 bytes long."

Star is able to support multi-volume archives with the posix pax format.

Check http://cdrecord.berlios.de/old/private/man/star.4.html for a description
of the POSIX compliant extensions star uses.

Note that I did already mention the star extensions in this list in october 
2003.

The reason why GNU tar has problems is related to the fact that the way GNU tar
deals with multi volume is not optimal. Also note that with the GNU tar method,
it is not possible to _create_ multi volume archives at all if the archive
program implements a FIFO for better throughput as star does.

Jörg

-- 
 EMail:address@hidden (home) Jörg Schilling D-13353 Berlin
       address@hidden           (uni)  
       address@hidden   (work) Blog: http://schily.blogspot.com/
 URL:  http://cdrecord.berlios.de/old/private/ ftp://ftp.berlios.de/pub/schily